Here's why:
* GPA is a weighted average: Your GPA isn't just an average of your letter grades. It's a *weighted* average, meaning each grade is multiplied by the number of credit hours for that course. Then, all the weighted grades are added together and divided by the total number of credit hours taken.
* Example: A 4-credit-hour course carrying an A (4.0) will have a much greater impact on your GPA than a 1-credit-hour course carrying an A (4.0). Both contribute positively, but the 4-credit course contributes four times as much to the final GPA calculation.
Therefore, there's no single answer to how much a major grade affects your GPA. It depends entirely on the course's credit hours and your grade in the course relative to your other grades.